Metallurgical apparatus – Process – Plugging or tapping
Patent
1997-03-05
1998-02-17
Kastler, Scott
Metallurgical apparatus
Process
Plugging or tapping
222590, 222594, 222597, 266230, 266271, B22D 4144
Patent
active
057184151
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates to a molten metal handling vessel and particularly to a means of improving the opening of the outlet nozzle of the vessel containing molten metal to allow the metal to flow out. The invention is especially, concerned with the teeming of molten steel from a ladle and, although not intended to be limited thereto, it will be more specifically described below with, reference to ladles.
In the steel industry, ladles are used to transfer molten metal from the melting and refining vessels to continuous casters or an ingot teeming bay The metal flow from the ladle is controlled typically by a slide gate valve. Usually, the outlet nozzle area is filled with a refractory sand introduced from the top of the ladle to prevent steel freezing in the nozzle cavity before teeming commences. This is accomplished in a variety of ways, either manually or semi-automatically.
However, all conventional methods have been found to be inconsistent and usually result in number of failures to open. The term "free open" refers to a totally successful opening without the need to flush the nozzle with oxygen to break the formed steel/sand skull. Free opening success rate varies from mill to mill but is usually in the range 80-90%. At the end of the cast, the ladle is closed by visually observing slag in the tundish or by detecting slag using devices sensitive to slag transfer.
At the lower levels of steel in the vessel, vortex formation can occur resulting in significant slag carry-over or the need to carry sizeable quantities of steel in the ladle at the end of teeming. Slag carry-over causes a variety of problems at the caster which usually result in quality problems as well as causing difficulties with consistent repeating of the ladle and filling sequence.
It is an object of the invention to provide an improved means of opening the outlet nozzle of a molten metal handling vessel particularly a ladle, whereby the free opening success rate may be increased.
Accordingly, in one aspect the invention provides a flow control device for the outlet nozzle of a molten metal handling vessel, the device being shaped to fit as a plug in the outlet nozzle whereby a gap is defined between the device and the closure means for the outlet, the device having apertures closed by means that melt under the influence of the molten metal in the vessel, the apertures providing passageway for the molten metal from the vessel to the outlet.
The means to close the apertures may be vented steel plates that melt under the influence of the molten metal--steel--with which the vessel is filled.
The flow control device is preferably a press-fit into the top portion of a suitably contoured ladle inner nozzle and may be a disposable item that is discarded after each teeming of the ladle.
The gap between the device and the closure means of the vessel, i.e. usually a slide gate valve in a ladle, may be filled with sand which may be blown into the gap through the open slide gate valve, preferably while the empty ladle has been rotated to its horizontal position, i.e. normal to its vertical metal-containing position. The slide gate valve may then be closed and the ladle rotated to its normal vertical position to be filled with molten metal.
Accordingly in another aspect the invention provides a method of teeming a molten metal handling vessel in which a flow control device is fitted as a plug into the outlet nozzle of the empty vessel, whereby a gap is defined between the device and the closure means for the outlet, the device having apertures closed by means that melt under the influence of molten metal in the vessel, the gap is filled with sand through the closure means for the outlet, the closure means is closed and the vessel is filled with molten metal, whereby the molten metal melts the means closing the apertures of the device, and the outlet closure is opened to teem the vessel.
The flow control device preferably comprises a head portion containing the apertures and a tail portion shaded to be a clos
REFERENCES:
patent: 743549 (1903-11-01), O'Connor
patent: 4913314 (1990-04-01), Otsuka et al.
patent: 5083754 (1992-01-01), Russo
patent: 5164098 (1992-11-01), Brown et al.
Foseco International Limited
Kastler Scott
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